The utilization of mechanical tissue fastening instruments, notably, open and endoscopic surgical staplers have been increasing steadily in recent years as a substitute for suturing in joining a tissue, joining and cutting a tissue simultaneously and performing anastomosis of tubular organs belonging to the digestive system in a number of surgical disciplines. Over the years these instruments have proven to provide significant clinical benefits of improved patient outcome in addition to procedural benefits of reduced procedure time and simplified surgical tasks when compared to laborious and time consuming suturing, and related cost savings. In certain types of surgical procedures use of surgical staplers has become the preferred method of joining a tissue including the bariatric, thoracic and colorectal surgeries.
There are several known types of surgical stapler instruments specifically adapted for use in various procedures such as end-to-end anastomosis, gastrointestinal anastomosis, endoscopic gastrointestinal anastomosis, and transverse anastomosis. Examples of stapler instruments for these various procedures can be found in U.S. Pat. Nos. 5,915,616; 6,202,914; 5,865,361; and 5,964,394, which are each herein incorporated by reference.
Known endoscopic surgical stapler instruments comprise a handle and an end effector that are fixedly attached to either ends of an elongate shaft and operatively engaged with each other. An end effector simultaneously makes a longitudinal incision in tissue and applies lines of staples on opposing sides of the incision. An end effector includes a pair of opposed jaw members that, if the instrument is intended for endoscopic or laparoscopic applications, are capable of passing through a cannula passageway. One of the jaw members, often referred to as a cartridge jaw member, receives a staple cartridge having at least two laterally spaced rows of staples in an elongate cartridge channel or a cartridge bay. The other jaw member, often referred to as an anvil jaw member, defines an anvil having staple-forming pockets aligned with the rows of staples in the staple cartridge. The instrument commonly includes a plurality of reciprocating wedges which, when driven distally, pass through openings in the staple cartridge and engage drivers supporting the staples to effect the firing of the staples toward the anvil.
In surgical stapling operation a physician operator first positions the end effector of a surgical stapler instrument to capture a target tissue between the two jaw members in open position and then operates the handle to close the two jaw members to clamp and compress the target tissue to a nominal thickness defined by the gap distance between the tissue contacting surfaces of the staple cartridge and the anvil prior to the firing of the staples. In the designs of presently available stapler instruments a physician has no means to control the degree or force of target tissue compression but is presented with a set of standardized staple cartridges colored coded according to the formed height(s) of staples contained therein, which correlates with the gap distance between the tissue contacting surfaces of the stale cartridge and anvil. Presently, the standardized set of staple cartridges, typically color coded white, blue, gold, green and black in the ascending order of staple heights contained therein, includes staples with formed heights between 1 mm and 2.3 mm in discrete increment. There are also in the market a set of staple cartridges, each cartridge containing a combination staples of varying heights with its own unique color coding tailored for application on tissue with varying compressed thickness. In compressing the target tissue the two jaw members comprising the end effector of stapler instrument are subject to a distributed reactionary load from the compressed tissue usually resulting in deflection of the two jaw members increasing progressively along the length thereof going from the proximal to distal end and more so, in the anvil than in the cartridge jaw member which is more substantial and structurally rigid. The corresponding variation in the gap distance between the tissue contacting surfaces of the staple cartridge and the anvil makes the tissue compression non-uniform decreasing progressively going from the proximal to distal ends of the end effector.
The level of tissue compression is one of the key factors that determine success of a surgical stapling operation often defined by adequate hemostasis and minimal damage of tissue along the staple line, and leak-free sealing of the target tubular organ among other considerations. It is known that a desirable clinical outcome of a surgical stapling operation is most likely achieved when the target tissue is compressed to a compression force between 6 g/mm2 or 8 g/mm2. Since present surgical stapler technology does not provide means to control the compression force of the target tissue a physician needs to choose a staple cartridge out of a standard set that would best approximate the optimal compression force for the target tissue when the two jaw members are closed with the chosen staple cartridge mounted in the cartridge bay. Having no practical means to help direct selection of staple cartridge, for example, accessory tools to directly assess a key mechanical property or condition of the target tissue, a physician is left to rely solely on his or her experience, or educated guess in selecting a staple cartridge, which leaves open possibility of under- or over-compression of the target tissue. Under-compression of tissue could lead to inadequate hemostasis and potential leakage of content contained within the tissue while over-compression to tearing of tissue or ischemia requiring prolonged period of healing. The staple cartridge selection is particularly difficult for a target tissue belonging to an organ with naturally occurring, large thickness variation such as in the stomach or an organ with unknown variation in mechanical properties such as in the lung at different disease state.
Manufacturers of present surgical stapler instruments instruct a physician to verify the adequacy of selected staple cartridge in compressing a target tissue by the feedback force felt in the hand operating the handle of the stapler instrument to apply the tissue compression. The instructions basically say to switch to a new staple cartridge with staples of larger formed height if it is overly difficult to operate the handle to apply compression to the target tissue specifically to guard against over-compression. This method is proven to be hardly practical in the field because the feedback force felt in the palm of the physician's hand may not necessarily correlates with the level of tissue compression due to the facts that the feedback force may be distorted being passed down through mechanical linkages and joints comprising the operating mechanism for the end effector and that the two jaw members comprising the end effector undergoes deflection caused by the reactionary load from the compressed tissue. In addition a unit of change in the compressed tissue thickness represented by the standard set of staple cartridges typically corresponds to only around few tens of gram of force in tissue compression which is barely discernible by the haptic sense felt in the palm of the hand alone even under the best of circumstances. Corresponding instruction for staple cartridge selection for preventing under-compression of a target tissue does not even exist.
U.S. Pat. No. 8,893,946 to Boudreaux et al., which is herein incorporated by reference, describes a surgical instrument that includes components for measuring the thickness of a tissue clamped between the two jaw members of an end effector thereof relying on a strain gauge or strain gauges as a means to generate a signal or signals corresponding to the tissue thickness and/or a compression load applied to the tissue. This disclosure describes the strain gauges as being used stand-alone but fails to describe how the strain gauges are practically implemented, for example, in the form of a load cell, well known to those of skill in the art, to generate such signals that could be converted to the thickness of tissue or the compression load acting thereon. The surgical instrument in this disclosure does not include any means to prevent or compensate for the potential deflection of a jaw member comprising an end effector as a result of a reactionary load from the compressed tissue nor for the effect of the play present in the closure mechanism of the two jaw members comprising the end effector on the tissue thickness measurement. This disclosure also fails to define the thickness of the clamped tissue in such sufficient detail for it to be of practical use in the selection of a staple cartridge for a stapling operation on the tissue.
Therefore, significant needs exist for a surgical device and method that would aid a physician in selecting a staple cartridge from the standard set of staple cartridges.